21500442 has 24 divisors (see below), whose sum is σ = 47111220. Its totient is φ = 7085760.

The previous prime is 21500431. The next prime is 21500443. The reversal of 21500442 is 24400512.

It can be written as a sum of positive squares in 2 ways, for example, as 21261321 + 239121 = 4611^2 + 489^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21500443) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5109 + ... + 8312.

Almost surely, 2^21500442 is an apocalyptic number.

21500442 is an abundant number, since it is smaller than the sum of its proper divisors (25610778).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21500442 is a wasteful number, since it uses less digits than its factorization.

21500442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13518 (or 13515 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21500442 is about 4636.8569095886. The cubic root of 21500442 is about 278.0667938119.

Adding to 21500442 its reverse (24400512), we get a palindrome (45900954).

The spelling of 21500442 in words is "twenty-one million, five hundred thousand, four hundred forty-two".